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Ceph Block Device

.. index:: Ceph Block Device; introduction

A block is a sequence of bytes (often 512). Block-based storage interfaces are a mature and common way to store data on media including HDDs, SSDs, CDs, floppy disks, and even tape. The ubiquity of block device interfaces is a perfect fit for interacting with mass data storage including Ceph.

Ceph block devices are thin-provisioned, resizable, and store data striped over multiple OSDs. Ceph block devices leverage :abbr:`RADOS (Reliable Autonomic Distributed Object Store)` capabilities including snapshotting, replication and strong consistency. Ceph block storage clients communicate with Ceph clusters through kernel modules or the librbd library.

.. ditaa::

            +------------------------+ +------------------------+
            |     Kernel Module      | |        librbd          |
            +------------------------+-+------------------------+
            |                   RADOS Protocol                  |
            +------------------------+-+------------------------+
            |          OSDs          | |        Monitors        |
            +------------------------+ +------------------------+

Note

Kernel modules can use Linux page caching. For librbd-based applications, Ceph supports RBD Caching.

Ceph's block devices deliver high performance with vast scalability to kernel modules, or to :abbr:`KVMs (kernel virtual machines)` such as QEMU, and cloud-based computing systems like OpenStack and CloudStack that rely on libvirt and QEMU to integrate with Ceph block devices. You can use the same cluster to operate the :ref:`Ceph RADOS Gateway <object-gateway>`, the :ref:`Ceph File System <ceph-file-system>`, and Ceph block devices simultaneously.

Important

To use Ceph Block Devices, you must have access to a running Ceph cluster.

.. toctree::
        :maxdepth: 1

        Basic Commands <rados-rbd-cmds>


.. toctree::
        :maxdepth: 2

        Operations <rbd-operations>


.. toctree::
        :maxdepth: 2

        Integrations <rbd-integrations>


.. toctree::
        :maxdepth: 2

        Manpages <man/index>


.. toctree::
        :maxdepth: 2

        APIs <api/index>